AI is Coming to a Crimp Connection Near You: Who Knew?
I have a modest confession to make; even in this day of sophisticated, tiny connectors and their cable assemblies, I still like to use crimped connections in many applications if appropriate. However, I might be leaning on the cutting edge as NASA has developed a non-destructive crimp test tool that may be the forerunner of artificial intelligence (AI) being applied to crimp tests.
While crimp connectors may not be suitable for RF work, they are still a viable solution for basic power, switch-closure (dry) circuits, and low-frequency work. Using them, it’s easy to make connections as needed “on the spot”. They don’t require soldering in awkward places or settings, they are reliable, and their connectivity, as well as signals, are easy to check without removal or cable stripping. What’s not to like?
I even used them recently in an upgrade of a three-zone home thermostat system, replacing an impenetrable “rat’s nest” of haphazard wiring with sets of clean, neat, labeled terminal strips and wires with spade-lug terminations (Figure 1). The on-site fabrication and installation of the 50-plus terminated wires was quick, clear, and easily checked. Plus, it will be easy to upgrade or troubleshoot in the future if there’s a need to do so.
Figure1: The original accumulation or wiring in this “rat’s nest” for a three-zone thermostat (left) was easily and cleanly replaced using on-site crimped spade lugs and wiring (right). (Image source: Bill Schweber)
I’m not the only one who stills sees a role for this “ancient” termination, either. A quick look shows thousands of such crimp terminations in various styles (spade, ring, quick disconnect) for different wire gauges, in various colors, along with manual plier-like crimping tools as well as power crimpers and dies. Molex even has its 76650-0040 connector kit with connectors and crimp tool. Further, you don’t even have to make the cables yourself as they are available in hundreds of commonly used lengths and terminations as stock items, and getting non-standard ones made up on the outside by a contractor is a routine procedure.
Figure 2: The 76650-0040 connector kit includes a wide variety of crimp terminals (spade, ring, quick disconnect) in various colors and sizes to accommodate different wire gauges; the hand crimping tool enables portable, low-volume crimping for convenience. (Image source: Molex)
Tool provides non-destructive crimp connection test
There is still one problem with crimped connections, as with many other terminations: doing a thorough mechanical and electrical test in addition to basic continuity. Even if the connection passes that simple test, the termination may have one or more imperfections to eventually go bad. Such as unevenly applied crimping force, misaligned wire, too much pressure (which can induce minute cracks in the wire), too little pressure (which often leads to an intermittent connection due to vibration), or moisture ingress and subsequent corrosion.
Testing the quality of a crimped connection by disassembling it or by giving it a pull-to-failure test isn’t a solution, because that destroys the connection under test. In a way, it’s like testing fuses: you can only test them by production-based sampling and destroying a unit under evaluation. Clearly, that is not practical for crimped connections as many of the cable assemblies are fabricated only in low volume for a specific installation. So how do you test these connections in a fast and non-destructive fashion?
That’s an issue that NASA’s Langley Research Center took very seriously, and its solution is elegant: a real-time, ultrasonic-based unit that uses advanced signal analysis to decide pass/fail (Figure 3). The system—which is available for licensing—sends an acoustic wave through the crimp assembly as it is being made.
Figure 3: This handheld tool uses ultrasonic techniques to evaluate the integrity of a crimped connection as it is being made. (Image source: NASA)
NASA’s summary report, Rapid and Verified Crimping for Critical Wiring Needs, notes that “…as the applied pressure increases and the crimp terminal deforms around the wire, the ultrasonic signature passing through the crimp is altered. The system analyzes the changes in the signal, including the amplitude and frequency, as an indication of the quality of both the electrical and mechanical connection between the wire and terminal. Various crimp quality issues such as under-crimping, missing wire strands, incomplete wire insertion, partial insulation removal, and incorrect wire gauge have been tested using this technique” (Figure 4).
Figure 4: The NASA analyzer can check the crimped connection in real-time and provide a pass/fail grade versus multiple possible shortcomings. (Image source: NASA)
You have to admire the sophisticated and apparently effective method they developed to assess the crimp quality, yet in a way that is fairly easy for the user to implement. Even better, it’s not done after the fact, but as the crimp is being made. If there is a problem with the crimp, the operator can stop and find out what’s going wrong before any more defective ones are made. If the connection passes, the wire can be attached immediately to the terminal if desired, thus eliminating the need to handle cables (often in unwieldy bundles) afterward. NASA’s fact sheet on the approach gives more information and the patent numbers for the technique.
This ultrasonic-based signature-analysis approach is yet another case of testing using accumulated data to define a pass/fail profile, rather than just using a single number or set of numbers. I suspect that as we collect more data, we will have the ability to integrate small, low-cost instrumentation (here, the ultrasound transceiver), and develop performance profiles and smart algorithms. We will definitely see more of this approach to testing using small-scale teachable algorithms (dare we call it “AI”?). There are many cases when measuring just a single number may be inadequate. Fortunately, we now have more powerful tools to make use of the accumulated data.